As one of the most challenging environmental issues, the effects of GHG emissions are integral to the understanding of a project’s impact and needs to be factored into the decision making process accordingly. At the same time a focus on proportionate assessment is also important in avoiding undue burden to developers and regulators. It is widely recognized that EIA should focus on a project’s significant impacts.
A ‘good practice’ approach is therefore advocated where GHG emissions are always considered and reported but at varying degrees of detail depending on the EIA project. This is important to build up sufficient knowledge and understanding of how to effectively assess GHG emissions.
During a project’s execution, an emissions and discharges report is produced to estimate the cumulative quantitative GHG emissions during the duration of the operating life. The emissions and discharges report may include the simulation of alternative cases to help support the design selection as Best Available Techniques (BAT).
BAT aims at achieving environmental ALARP by ensuring innovation and implementation of state-of-the-art technologies as far as it is technically and economically feasible for the specific project. The BAT assessment methodology shall be used as a tool throughout the design phase to justify the proper selection of the design, systems and equipment. BAT assessments are one method to demonstrate that negative environmental impacts are mitigated to, as far as reasonably practicable.
The general assessment shall be based on emission factors of the region:
The BAT Assessment shall be performed according to a step-wise process:
The first step includes a screening of available alternatives. During a workshop, or as a desktop exercise, alternatives are listed and a high-level evaluation of the implications in terms of environmental performance, technical applicability and economic availability is carried out. This evaluation may be based on Client’s input, publicly available information, vendor data, or experience from previous projects. The aim of the screening step is to establish a short list of alternatives that may be studied and compared in more detail. Only those alternatives that are deemed to perform best from the environmental perspective, while being technically and economically feasible are selected.
The next step is an in-depth evaluation of each alternative. It consists of an estimation of the resource use, emissions and discharges, including waste generation and reuse/recycling potential for each alternative. At this stage it is important to clearly define the boundaries of the system since this will form the basis for the comparison of alternatives on the environmental basis. It is equally important to select the right parameters for which the environmental performance is to be measured against.
The alternatives are then ranked based on their environmental performance. In some cases, it is necessary to establish a trade-off between different environmental performance parameters, for example between oil in water content and energy use for a produced water treatment system; a treatment system may be very efficient in removing oil particles from the water, but the process might be very energy intensive.
Once alternatives are ranked according to the environmental performance, the technical implications of each alternative are investigated. Typical technical constraints include space and weight, the techniques availability and maintainability, consequences on the safety level (e.g. due to use of gas or pressurized steam), and the technical compatibility with the overall design. Alternatives may then be ranked on the technical criteria, or simply being defined as “technically feasible” or “not technically feasible”.
The next activity in step two is to investigate the economic availability for each alternative. This should involve an evaluation of the capital expenditure (CAPEX) and also operational expenditure (OPEX). CAPEX may be established based on vendor quotes or data from previous projects. OPEX should include maintenance costs, potential repair or replacement costs, but also costs linked to emissions. Similar to the technical criteria, alternatives are then ranked according to their costs.
Finally, in step 3 the alternatives are compared, and the best available technique is established. The aim is to determine the best compromise between environmental performance, technical feasibility and economically viable where the highest weight is given to the environmental performance.
